This invention relates to an LED (Light Emitting Diode) lamp module provided by thermally connecting a surface-mounted type LED lamp having an LED chip mounted on a ceramic package to a radiator plate.
A surface-mounted type LED lamp having an LED chip mounted on a package is mounted on a wiring board made up of glass epoxy and metal of Cu (copper), Al (aluminum), or the like, through solder, whereby an LED lamp module is provided for use with a lighting system, or the like. (For example, refer to Patent Publication No. 2004-505172) White resin, ceramic, or the like, is used as a material of the package. A package made of white resin discolors because of aged deterioration of the white resin and involves a problem of degradation of the light output efficiency. Thus, often a ceramic package free from aged-deterioration is used for applications when high quality is required.
However, to mount an LED lamp on the above-mentioned wiring board, the thermal expansion difference between the ceramic and the wiring board is large and the stress imposed on solder becomes very large. Thus, a crack occurs in the solder in a short time in an environment in which the temperature difference is severe, and a break may occur between the LED lamp and the wiring board. Particularly, when a metal base with high thermal conductivity is used as a radiation measure against heat generated during the LED chip driving, the above mentioned stress problem becomes apparent due to enlarged thermal expansion difference. For such a reason, it is difficult to make full use of the high quality of a ceramic package.
It is therefore an object of the invention to provide an LED lamp module for improving the joint property of an LED lamp using a ceramic package and a wiring board and enhancing the radiation performance of the LED lamp.